What is the difference between "Deliver (server)" operation and "Deliver Phase 2" one?

Kubota-san:

I found this article:

Source control process recipes for Rational Team Concert
https://jazz.net/library/article/1193

Deliver (server)

The Deliver (server) operation runs on the server before change sets are added or removed from a component.

The operation is run on the set of change sets that are being added to (or removed from) a component, which is computationally less expensive than the subsequent Deliver Phase 2 (server) operation.

Deliver Phase 2 (server)

The Phase 2 delivery operation occurs before a deliver, but after the server has calculated the computationally intensive before/after states of each item that will be modified.

Amano-san,
Thanks for your prompt response.
Actually I have posted same question redundantly.
https://jazz.net/forum/questions/140599/what-is-the-difference-between-deliver-server-operation-and-deliver-phase-2-one?page=1&focusedAnswerId=140623#140623